Types of Nerves in the Human Body

Our brains are larger than any other animal's, relative to our body mass, but they're still made of the same types of nerves. The same is true of our peripheral nervous system, which is composed of the same types of motor, sensory and autonomic nerves as other members of the animal kingdom.

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The nerves of the brain, neurons, can be thought of as information relays. They don't gather sensory information and neither do they directly command bodily movements. Instead, they store memories and process new information, which is then used to dictate actions throughout the body. Neurons have three main parts: the soma, dendrites and axon. The soma is the body of the cell, which contains the DNA and vital organelles. The dendrites gather input from other nerves, while the axon relays electrical signals onward. Neurons come in two main types. One type excites other neurons, and when it is activated it compels other neurons to activate, too. The other type releases an inhibitory signal when it's activated, discouraging other neurons from activating.

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Neurons ultimately link to the muscular system, and the motor nerves are the bridge between the two. They receive electrical impulses through their dendrites, just like neurons, but instead of an axon connecting with our nerves, the motor nerves connect with muscles. When they release an impulse, it causes the muscle to contract, which in turn moves the various parts of the human body.

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There are many different types of sensory nerves. The skin has nerves that are sensitive to temperature, pressure and pain. The eyes have rods and cones which detect light and color, respectively. The ear relays auditory information along the massive cochlea nerve. These sensory nerves have axons which they use to communicate with neurons, but instead of dendrites, they're excited by signals from their sensory apparatus. For instance, a retinal rod is excited when touched by light, which causes it to send a signal along its axon to neurons within the brain.

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The autonomic nervous system is composed of the same types of neurons and motor nerves found throughout the human body, but it operates by different rules. Instead of relying upon sensory input from the outside world, it automatically works through its own cycles. Many internal organs are regulated through the autonomic nervous system, including the heart. A weakening of the autonomic nervous system can have serious health consequences.